Clinical Significance of Low Density Lipoprotein Cholesterol Measurements: Direct Versus Indirect Method

Abstract

Introduction: Estimation of low density lipoprotein cholesterol (LDL-C) is crucial in management of coronary artery disease patients. The management of dyslipidemia is largely based on the concentration of LDL-C. The objective of this study was to compare direct measurement of LDL-C determined by a homogenous method with LDL-C estimation done by Friedewald formula (FF) in heterogeneous populations.

Methods: In this cross sectional study, we measured LDL-C by homogenous method (D-LDL-C) in 1,000 fasting samples & compared with FF (F–LDL-C) used for calculation of LDL-C. The measurements of total cholesterol (TC) and triglycerides (TG) were performed using traditional enzymatic methods. The measurements of high density lipoprotein cholesterol (HDL-C) and LDL-C were performed using direct methods with precipitation, and the estimation of the LDL-C fraction was calculated using the FF.

Results: Correlation analysis shows that the two methods had significant correlation (p<0.0001). However the FF had positive bias in regard to direct method with TG levels ≤150 mg/dL. No bias was observed between the methods for TG levels from 151-200 mg/dL & from 201-300 mg/dL. Whereas, TG levels from 301-400 mg/dL shows negative bias by FF.

Conclusion: The Friedewald’s formula does not shows homogenous performance for estimating LDL-C levels in samples with different TG levels as compared with that of direct method.